Gas filled discharge tube control system



Oct, 31, 1933. F. w. scHRAMM 1,932,606

GAS FILLED DISCHARGE TUBE CONTROL SYSTEM Filed June 11, 1932 INVENTOR BYX ATTORNEY Z W. Sc/umumm' Patented Oct. 31, 1933 GAS FILLED DISCHARGETUBE CONTROL SYSTEM Fred. W. Schramm, East Orange, N. J., assignor toAmerican Telephone and Telegraph Company, a corporation of New YorkApplication June 11, 1932. Serial No. 616,729

10 Claims.

This invention relates to electrical circuits and more particularly toimproved means whereby the current in one circuit may be utilized tocontrol the impedance in another circuit connected to the first circuitby a gas filled tube, such for example, as a discharge tube filled witha gas such as neon.

Gas filled discharge tubes have the characteristic that the resistancebetween the cathode and anode elements may be changed from a high valueto a comparatively low value when the gas is ionized and an arc isestablished therein by current applied thereto. Accordingly, a circuitcompleted over the cathode and anode elements of such a gas filled tubemight have its impedance controlled by current applied to the tube overanother circuit. Under such conditions the gas filled tube will performmany of the functions of an electromagnetic relay, such as effectivelyopening and closing the circuit to be controlled.

The arrangements of the invention are particularly applicable to systemsof the above type in which alternating current is used to supply thevoltage for the cathode-anode circuit of the gas filled tube and has forits primary object the provision of means for rendering the operation ofthe tube less intermittent and more steady in character than heretofore.

In systems utilizing gas filled discharge tubes to perform the functionsof a switch or as a circuit controlling element the resistance of thepath between cathode and anode is comparatively high when an arc is notestablished between said elements and drops to a few ohms during arcingperiods. When direct current is used for the anode supply, this pathremains at the low value during the whole time that the arc isestablished. However, when alternating current is used for the anodesupply, as for example, to provide a self-quenching arrangement or forother reasons, the arc begins only when the anode is positive and thepotential is somewhat higher than the arc-drop of the gas employed (inthe neighborhood of 20 volts for the gases ordinarily used). The are isquenched when the voltage again drops below this value and remainsquenched during the entire negative half-cycle of the supply current. Asa con- 50 sequence, the average value of resistance of the cathode-anodepath over a complete cycle of anode voltage is considerably higher thanthe value obtained when direct current anode supply is used. If thecircuit to be controlled through the arc path is a direct currentcircuit, a condenser or filter must usually be provided to maintain thecurrent flow during the quenched periods or, in other words, to preventmodulation at the supply frequency in the controlled circuit.

The arrangements of the invention provide means whereby an alternatingcurrent anode supply may be used and the average value of resistance ofthe cathode-anode path over a complete cycle of anode voltage will besubstantially as low as when direct current anode supply is used. Thearrangements of the invention accomplish their objective by shorteningor eliminating the quenched periods of the are when alternating currentanode supply is used. Other objects and features of the invention willappear more fully from the detailed description thereof hereinaftergiven.

The invention may be more fully understood from the followingdescription together with the accompanying drawing in the Figures 1 to'7 of which the invention is illustrated.

Fig. 1 is a circuit diagram embodying the invention. In Fig. 2 are showncurves illustrating principles of operation of the invention as shown inFig. 1. Fig. 3 shows a modification of Fig. 1. Fig. 4 is a circuitdiagram emcodying a modification of the invention. In Fig. 5 are showncurves illustrating principles'of operation of the invention as shown inFig. 4. Fig. 6 is a circuit diagram embodying a further modification ofthe invention. In Fig. '7 are shown curves illustrating principles ofoperation of the invention as shown in Fig. 6. Similar referencecharacters have been utilized to denote like parts in all of thefigures.

In Fig. l is shown a circuit L11 connected to the grids of the gasfilled discharge tubes V1 and V2. The gaseous content of these tubesmay, for example, be neon or some similar gas. These tubes have thecharacteristic that the gas will ionize and current will fiow from anodeto cathode at a certain grid voltage, and when in this condition willhave a very low resistance between cathode and anode instead of a .veryhigh resistance, as when unoperated. A circuit L12 is shown connected tothe anodes and cathodes of the tubes. The impedance of circuit L12 maybe controlled by the operation of the tubes by the current applied overline L11. The grids of the tubes V1 and V2 are connected in parallel incircuit L11 and the anodes thereof are connected in parallel in thecircuit L12. Alternating current is utilized to supply the potential forthe anodes by means of the circuit L13 and the transformer 4.

It will be noted that by means of the arrangement of the secondarywindings of transformer 4 a push-pull connection is provided for thealternating current anode supply. In other words, during one half-cycleof the current a positive potential will be applied to the anode of oneof the tubes and during the other half-cycle a positive potential willbe applied to the anode of the other of the tubes. In such anarrangement an arc is established in one of the tubes for each halfcycleof the alternating current supply. The are in each tube during thepositive half-cycle will exist for all of the positive half-cycle exceptfor the short periods at the beginning and end of the half-cycle whenthe potential (depending on the gas employed) is less than that requiredto maintain the arc. The above described operation is indicated ingreater detail in Fig. 2. In the two upper portions of Fig. 2 the curvesshow the potentials applied to the anodes of tubes V1 and V2. Thesepotentials would be 180 out of phase. The shaded areas indicate theperiods during which arcs are established in each of the tubes. Asindicated by the shaded areas in the lower portion of Fig. 2, a pathwill be closed by the tubes V1 and V: for circuit L1, except during thevery short intervals X, Y and Z. With such an arrangement thecathode-anode resistance in series with circuit L1: would very closelyapproach the value which could be obtained by using direct current anodesupply.

The control circuit connected to the grids of the tubes V1 and V: isshown in Fig. 1 as including a transformer and a rectifying unitcomprising the rectifier 1, resistance 2, and condenser 3,

- to apply a direct current potential to the grids.

However, alternating grid potentials may be used if a frequencysufllciently higher than the anode supply is used to prevent beats. Witha control frequency at or near the anode supply frequency, completequenching will be obtained if the grid is negative at the time the anodeis positive and vice versa. The networks comprising condensers C1 andinductances L1 are provided as shown and are anti-resonant circuits atthe anode supply frequency. This prevents short circuiting thetransformer 4 while permitting the two anodes to be connected togetherfor the external circuits. The networks comprising L1 and C1 wouldaccordingly prevent alternating currents of the anode supply frequencyfrom flowing in circuit L1: but would permit direct currents to flowtherein. The networks comprising condensers C and resistances R areprovided as shown. Resistances R are chosen to be high enough toeffectively open the external circuit through the transformer center tapto the cathode. Condensers C provide a low impedance path aroundresistances R forthe alternating current anode supply. Since thecondensers C receive a charging current during the arcing interval, theresistances It also aid in dissipating the charges thereon during thequenched interval.

In Fig. 3 is shown a single tube V: having but a single grid and cathodebut with two anodes. This tube would provide the same features as thetwo tubes of Fig. l and the circuit arrangements in other respects aresubstantially similar.

In order to provide a constant arc-path over the whole alternatingsupply current cycle the arrangement shown in Fig. 4 might be used. Inthis arrangement a single gas filled discharged tube V4 would beprovided having four anodes A1, A2, B1 and B2. Current from thealternating source would be transmitted over circuit L1: to

the winding of transformer 4. Due to the arrangement of the secondarywindings of the transformer with respect to the anodes during eachhalf-cycle of the current the potentials applied at points such as P andQ would be 180 out of phase. This would cause the voltages on anodes A1and B1 to be 180 out of phase. In Fig. 5 the curves A'i and B1 show thevoltages on the anodes A1 and B1. The shaded areas indicate the periodsduring which an arc would exist in the respective anode circuits. Ifonly anodes A1 and B1 were provided, the effect would be substantiallythe same as in the arrangements of Figs. 1 and 3 and a series of smallgaps would exist in the are. For this reason the additional anodes A2and B2 are provided. The voltages on these anodes would for eachhalf-cycle of the supply current be 180 out of phase. However, thepotentials applied to the auxiliary anodes A2 and B: will, by virtue ofthe phase displace ment provided by In and Ca, lag in phase behind thepotentials applied to anodes A1 and B1, respectively, so that the arcsestablished through the circuits of anodes A: and B2 will be maintainedfor a suflicient period after the extinguishment of the arcs through thecircuits of anodes A1 and B1 to prevent the existence of any gaps in theare, such as shown in Fig. 2. Curves A'z and B: of Fig. 5 illustrate theabove principles of operation of anode circuits A2 and B2. Anexamination of the shaded areas of all the curves of Fig. 5 will showthat no gaps will exist between arcs in the various anode circuits andthat a constant arc-path for circuit L1: will be provided. The anodesA1, A2, B1 and B2 are all connected in parallel with each other incircuit L12. The networks comprising inductances L1 and condensers C1and the networks comprising resistances R and condensers C are provided,as in the previous figures, to separate the alternat ing and directcurrent paths and to prevent the short circuiting of transformer 4. Ashereto fore pointed out the inductances L3 and condensers C3 each form acircuit which provides a voltage drop across C3 lagging behind thevoltage applied to anode A1 or anode B1. Resistances R3 are provided tosimulate the resistances of In so that the resistance in the externalcircuit is the same through any arc-path.

In Fig. 6 is shown a further modification of the arrangements of theinvention. In this arrangement a single gas filled discharge tube V5 isprovided with three anodes A, B and C. A source of alternating currentis connected to circuit L14 and transformer 5 which will supplythreephase current to 'the anodes. The curves and shaded areas of Fig.'7 show the resulting overlapping of the arcing intervals in such anarrangement. The networks L1 and C1 and RC are provided as shown for thesame purposes as in the other figures. By increasing the number of anodecircuits of tube V5 other polyphase currents might be used for the anodesupply, if desired.

In the arrangements of the invention the gas filled discharge tubes mayeither be hot-cathode tubes, cold-cathode tubes, or tubes employingauxiliary elements, such as collectors," in their operation.Accordingly, while the invention has been disclosed as embodied incertain specific forms which are deemed desirable, it is understood thatit is capable of embodiment in many and other widely varied formswithout departing from the spirit of the invention as defined by theappended claims.

What is claimed is:

1. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having twoanodes connected in said controlled circuit, an altemating currentsource connected to said anodes so that when a positive potential isapplied to one anode a negative potential will be applied to the otheranode, and vice versa, and means in said controlling circuit forapplying a direct current voltage to the grid of said tube.

2. A controlling circuit, a circuit controlled thereby, gas filleddischarge tubes interconnecting said circuits, the anodes of said tubesbeing connected in parallel in said controlled circuit, an alternatingcurrent source so connected to said anodes that when the applied gridvoltages in said tubes are identical and of a certain polarity an arcwill be established in one of said tubes for every half-cycle of currentapplied from said source, and means in said controlling circuit forapplying identical voltages of a certain polarity to the grids of saidtubes.

3. A controlling circuit, a circuit controlled thereby, gas filleddischarge tubes interconnecting said circuits, the anodes of said tubesbeing connected in parallel in said controlled circuit, an alternatingcurrent source for supplying voltages for said anodes, said source beingconnected in push-pull relationship to said anodes whereby when theapplied grid voltages in said tubes are identical and of a certainpolarity said tubes will discharge alternately, one tube discharging foreach half-cycle of current from said source, and means in saidcontrolling circuit for applying identical voltages of a certainpolarity to the grids of said tubes.

4. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having aplurality of anodes connected in said controlled circuit, an alternatingcurrent source so connected to said anodes that voltages 180 out ofphase with each other will be simultaneously applied to said anodes, andmeans in said controlling circuit for applying to the grid of said tubea direct current voltage of a certain polarity.

5. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having aplurality of anodes connected in said controlled circuit, means forsimultaneously applying to said anodes voltages having opposing phaserelationships, and means in said controlling circuit for applying to thegrid of said tube a direct current voltage of a certain polarity.

6. A controlling circuit, a circuit controlled thereby, a gas filleddischarge, tube interconnecting said circuits, said tube having aplurality of sets of anodes connected in said controlled circuit, meansfor simultaneously app to the anodes of one or said sets equal voltagesopposite in phase with respect to each other, means for simultaneouslyapplying to the anodes of another of said sets equal voltages oppositein phase with respect to each other but lagging behind in phaserelationship with respect to said first mentioned voltages, and means insaid controlling circuit for applying to the grid of said tube a directcurrent voltage of a certain polarity.

'7. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having threeanodes connected in said controlled circuit, a source of polyphasecurrent for simultaneously supplying voltages to said anodes, and meansin said controlling circuit for applying to the grid of said tube adirect current voltage of a certain polarity.

8. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having aplurality of anodes connected in parallel in said controlled circuit, analternating current source for supplying voltages for said anodes, atransformer for connecting said source in push-pull relationship to saidanodes whereby voltages opposite in phase will simultaneously be appliedto said anodes, networks associated with the anode. circuits of saidtube for preventing direct currents from said controlled line from beingtransmitted through said transformer circuit and for preventingalternating currents from said source from being transmitted out oversaid controlled line, and means in said controlling circuit for applyingto the grid of said tube a direct current voltage of a certain polarity.

9. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having a cathodeand a plurality of anodes connected in said controlled circuit, analternating current source, means for so associating said source withsaid anodes that at any instant at least one of said anodes is always ata positive potential with respect to said cathode, and means in saidcontrolling circuit for applying to the grid of said tube a directcurrent voltage of a certain polarity.

10. A controlling circuit, a circuit controlled thereby, a gas filleddischarge tube interconnecting said circuits, said tube having a gridand a cathode and a plurality of anodes connected in said controlledcircuit, an alternating current source,-and means for so applying saidsource to said controlled circuit that for a certain condition of gridvoltage a continuous arc-path will be established in said tube and foranother condition of grid voltage the arc-path in said tube will beextinguished.

' FRED. W. SCHRAMM.

